Rock & Mineral Encyclopedia
Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.
Labradorite
A plagioclase feldspar famous for labradorescence, a dramatic flash of iridescent blue, green, and gold across a dark gray stone.
mineral
Kyanite Schist
A mica schist containing bladed blue kyanite crystals, a marker of medium- to high-grade metamorphism of aluminous rocks.
metamorphic
Lignite
The lowest rank of coal, a soft brown carbon-rich rock formed from compacted peat, used mainly for electricity generation.
sedimentary
Khondalite
A high-grade metamorphic gneiss of garnet, sillimanite, quartz, and graphite, derived from ancient aluminous sediments.
metamorphic
Heliodor
The golden-yellow gem variety of beryl, colored by iron, prized for its bright sunshine hue and excellent durability.
gemstone
Hot Pink Tourmaline
An intensely saturated hot-pink to magenta elbaite tourmaline, among the most vivid and eye-catching of all pink rubellites.
gemstone
Green Garnet
An umbrella term for green members of the garnet group, including prized tsavorite, demantoid, and rare chrome-rich uvarovite.
gemstone
Granite
A coarse-grained, speckled intrusive rock built from quartz, feldspar, and mica, forming the bedrock of the continents.
igneous
Grape Agate
Clusters of tiny botryoidal chalcedony spheres resembling bunches of grapes, famously purple, found in Indonesia.
mineral
Geyserite
Porous opaline silica deposited around geysers and hot springs, often preserving delicate microbial textures.
sedimentary
Glaucophane Schist
A blue, high-pressure metamorphic schist rich in glaucophane, the classic rock of subduction zones, also known as blueschist.
metamorphic
Euxenite
A black rare-earth niobium-tantalum oxide, often radioactive and metamict, mined for yttrium, niobium, and associated rare elements.
mineral
Gabbro
A coarse-grained, dark mafic intrusive rock that is the plutonic equivalent of basalt, rich in plagioclase and pyroxene.
igneous
Flint
A hard, dark variety of chert that knaps into razor-sharp edges and sparks against steel, central to Stone Age technology.
sedimentary
Dumortierite Quartz
Quartz colored blue by inclusions of the mineral dumortierite, giving a denim-like blue ornamental stone harder than dumortierite alone.
gemstone
Desert Rose
A rosette-shaped cluster of bladed gypsum or barite crystals that traps sand, forming flower-like formations in arid deserts.
mineral
Dark Green Tourmaline
Deeply saturated green tourmaline colored by iron, often so dark it appears nearly black until viewed in bright light.
gemstone
Claystone
A very fine-grained sedimentary rock made mostly of clay minerals, smooth to the touch and lacking the gritty feel of siltstone.
sedimentary
Clear Beryl
Transparent, colorless beryl (goshenite), the pure form of the species valued for its clarity, hardness, and well-formed crystals.
gemstone
Chocolate Garnet
A rich brown variety of andradite (or grossular-andradite) garnet, marketed for its warm chocolate color and notable brilliance.
gemstone
Charnockite
A granite-like rock containing orthopyroxene, formed at high temperatures and pressures and often classed with the granulites.
igneous
Cat's Eye Obsidian
Sheen obsidian cut so that aligned microscopic inclusions produce a single moving band of light, a cat's-eye effect.
igneous
Cat's Eye Beryl
Beryl displaying chatoyancy, a bright moving band of light, caused by parallel tube-like inclusions when cut as a cabochon.
gemstone
Cat's Eye Aquamarine
Aquamarine that shows a bright moving band of light, or cat's eye, caused by parallel needle-like inclusions when cut as a cabochon.
gemstone